The present invention relates generally to semiconductor packaging, and, more particularly, to packaged semiconductor pressure sensor devices.
Semiconductor sensor devices, such as pressure sensors, are well known. Such devices use semiconductor pressure-sensing dies to sense the ambient atmospheric pressure. These dies are susceptible to mechanical damage during packaging and environmental damage when in use, and thus they must be carefully packaged. Further, pressure-sensing dies, such as piezo resistive transducers (PRTs) and parameterized layout cells (P-cells), do not allow full encapsulation because that would impede their functionality.
FIG. 1 shows a cross-sectional side view of a conventional package 100 having a substrate (e.g., a pre-molded lead frame) 102 upon which are mounted a micro-control unit (MCU) die 104, an acceleration-sensing die (G-cell) 106 using die-attach film or epoxy 110(1) and 110(2), respectively.
The MCU die 104 is wire-bonded to the substrate 102 with bond wires 112(1), and the G-cell 106 is wire-bonded to the MCU die 104 with bond wires 112(2). Mold compound 114 is applied over the substrate 102 to encase the G-cell 106, bond wires 112(1) and 112(2), and a portion of the MCU die 104. The space above the portion of the MCU die 104 that is not encased by the mold compound 114 forms a cavity 116.
After molding, a pressure-sensing die (P-cell) 108 is mounted inside the cavity 116 and on the MCU die 104 using a die-attach film or epoxy 110(3), and the die-attach film or epoxy 110(3) is cured by placing the partially assembled package 100 in an oven.
After curing, the P-cell 108 is wire-bonded to the MCU die 104 with bond wires 112(3), and the cavity 116 is filled with a pressure-sensitive gel material 118, which enables the pressure of the ambient atmosphere to reach the pressure-sensitive active region (not explicitly shown) on the top of the P-cell 108.
The above assembly process is not without difficulties. For example, (i) the mounting of the P-cell 108 is performed separately from the mounting of the MCU 104 and the G-cell 106, (ii) the curing of the die-attach film or epoxy 110(3) is performed separately from the curing of the die-attach film or epoxy 110(1) and 110(2), and (iii) the wire-bonding of bond wire(s) 112(3) is performed separately from the wire-bonding of bond wires 112(1) and 112(2). These separate mounting, curing, and wire-bonding steps add time and cost to the assembly process. Accordingly, it would be advantageous to have a more economical way to pressure sensor dies.